D250E Series II, D300E Series II, D350E Series II and D400E Series II Articulated Trucks Power Train Electronic Control System Caterpillar

Illustration 1	g00481473
Schematic Of The Relay For The Backup Alarm

This diagnostic code is recorded when the ECM reads the current of the relay circuit as above normal (short to ground).

The possible causes of this diagnostic code are listed:

• Wire 321-BR shorted to ground.

• The relay is faulty.

• The ECM is faulty. This is unlikely.

This diagnostic code causes the backup alarm to be OFF at all times. Ensure that CID 0144 FMI 06 is active for the backup alarm relay. The relay is connected to the ECM through wire (321-BR) to connector contact J2-37. The return wire (F790-PK) for the relay connects to the ECM through connector contact J2-3. The resistance of the relay coil is 360 ohms.

Note: The following test procedure may create other diagnostic codes. Ignore these created diagnostic codes and clear the diagnostic codes when the original diagnostic code has been corrected.

1. CHECK THE RELAY.

   1. Turn the key start switch to the ON position. DO NOT start the engine.

   2. Ensure that the CID 0144 FMI 06 is on hold.

   3. Observe the status of the "SERV CODE" indicator. "SERV CODE" will be showing or "SERV CODE" will not be showing.

   4. Disconnect the machine harness from the backup alarm relay.

      Expected Result: The "SERV CODE" indicator is no longer showing when the relay is disconnected.

      Results:

      • YES - The "SERV CODE" is no longer showing. Replace the relay. STOP.

      • NO - The "SERV CODE" remains. Proceed to Step 2.

2. CHECK THE RELAY FOR A SHORT TO GROUND.

   1. Turn the key start switch to the OFF position.

   2. Disconnect the machine harness from the relay.

   3. Disconnect the machine harness connectors J1 and J2 from the ECM.

   4. At the machine harness connectors, measure the resistance from the signal contact J2-37 (wire 321-BR) to all possible sources of ground.

      Expected Result: There should be greater than 5000 ohms resistance.

      Results:

      • OK - The resistance is greater than 5000 ohms. Proceed to Step 3.

      • NOT OK - The resistance is not greater than 5000 ohms. Check the +battery and ground circuits of the machine harness. Repair the machine harness or replace the machine harness. STOP.

3. CHECK IF THE DIAGNOSTIC CODE REMAINS.

   1. Inspect the harness connectors and clean the contacts of the harness connectors.

   2. Reconnect all harness connectors.

   3. Turn the key start switch to the ON position.

   4. Enter the service mode of the Caterpillar Monitoring System and clear all inactive diagnostic codes.

   5. Operate the machine.

   6. Check if CID 0144 FMI 06 for the relay is present. "SERV CODE" is showing.

      Expected Result: TheCID 0144 FMI 06 for the relay is NOT present. "SERV CODE" is NOT showing.

      Results:

      • NO - The diagnostic code remains active. It is unlikely that the ECM is faulty. Exit this procedure and perform this procedure again. If the cause of the diagnostic code is not found, replace the ECM. See Testing And Adjusting, "Electronic Control Module (ECM) - Replace". STOP.

      • YES - The diagnostic code is not present. The diagnostic code does not exist at this time. The initial diagnostic code was probably caused by a poor electrical connection or a short at one of the harness connectors that was disconnected and reconnected. Resume normal machine operation. STOP.